Ultima Demons sometimes have a small chance appearing at Midlight's Deep after completing it, meaning that if Ramza forgot to learn Ultima during some very limited opportunities in Chapter 4, he is able to learn it there
Its a cool mechanic here, but beware if you leave an army for your last adversary
It prevents the degenerate forced wheel loops we see with cards like Narset, Parter of Veils, but for the aggressive Red player who just emptied their hand to get an unblocked attacker through, its a three-mana reload thats almost impossible to pass up
Outside of a few very specific cards (which will be mentioned first) that require deck sizes above the minimum, all the other reasons you might want to are more fitting to casual magic: Battle of Wits - A win condition that specifically requires you to have more than 3 times the minimum deck size left in your deck to win means starting with about 4 times that minimum, if not more
This also acts as a great attack deterrent if you hold the equipped creature up as a blocker